A c/4 spaceship is a spaceship travelling at one quarter of the speed of light. The first such spaceship to be discovered was, of course, the glider, and this remained the only known example until December 1989, when Dean Hickerson found the first orthogonal example, 119P4H1V0, and also a new diagonal example, the big glider. For other examples see B29, Canada goose, crane, Enterprise, edge-repair spaceship, non-monotonic, Orion, quarter, sparky, swan and tagalong. It is known that c/4 is the fastest possible speed for a (45-degree) diagonal spaceship.
- Nathaniel Johnston (October 30, 2009). "Spaceship Speed Limits in "B3" Life-Like Cellular Automata". Retrieved on December 12, 2016.